Coastal wetlands play a critical role in maintaining the health of our planet by providing essential ecosystem services such as flood control, water purification, and critical habitat for a vast variety of species. However, their vulnerability to climate change and sea-level rise poses a significant threat to these services. Therefore, to provide long-term protection against erosion and sea-level rise, a shoreline restoration project was designed in coastal North Carolina (US) to use dredged sediments and rebuild the historic footprint of an eroded shoreline marsh adjacent to a regional airport's runway. To evaluate the potential benefits of this restoration project, the Sea Level Affecting Marsh Model (SLAMM) was employed. The developed model was run at a high spatial resolution (1m cell size) to investigate the effects of sea-level rise on the wetland communities and estimate the potential benefits of using dredged sediment to increase surface elevation. The results of the SLAMM model indicated that the restoration project offers substantial benefits in terms of shoreline marsh persistence through 2050, under all sea-level rise scenarios. This finding is significant because it shows that the restoration project can provide immediate benefits and help sustain the coastal wetlands in the face of sea-level rise. However, the benefits of the restoration project start to diminish after 2050, and differences among marsh areas in the restored and unrestored scenario decrease with increasing rates of sea-level rise. Therefore, it is essential to develop adaptive management strategies to ensure the long-term persistence of coastal wetlands and their ecosystem services. Overall, this study shows that the beneficial use of dredged sediments as a nature-based solution can effectively sustain coastal habitats threatened by sea-level rise and erosion.

A document by Ramin Familkhalili. Click on the document to view its contents.

Recent efforts to assess the ability of current salt marsh extent to persist over the next 50-100 years conclude that under intermediate sea-level rise (SLR) projections, salt marsh extent in North America will suffer a dramatic decline by 2100. This occurs as the rate of SLR reaches 12-14mm/y, exceeding the ability of most marshes to accrete sufficient sediment to keep up, and migration space becomes limited, eliminating the ability of marshes to move up. Increasing future marsh resilience by building or restoring marshes at higher elevations often comes with a contemporary decrease in the provision of some marsh ecosystem services, such as fishery use, denitrification, and primary production, which are optimal at mid to low marsh elevations. Current state and federal environmental laws and regulatory policy are designed to protect current salt marsh habitat, and prevent actions that result in a loss of habitat and associated ecosystem services. An approach that better balances the need to protect current marsh habitat with the need to ensure future marsh habitat is needed to create and restore resilient coastal wetlands. Marsh restoration and resilience projects should be evaluated over a 50-75 year time period, utilizing updated NOAA SLR predictions and spatial models incorporating projected SLR rates and migration space. Examples of marsh restoration and shoreline stabilization projects that provide long-term marsh resilience to SLR, but may reduce ecosystem services short-term, are provided from sites in North Carolina.